1. Field of the Invention
The present invention relates to a thermal management material for electronic devices. More particularly, the present invention relates to a composition of a thermal interface material.
2. Description of Related Art
As electronic products are being rapidly introduced to the market, not only these electronic products are desired to be light, thin, compact and small, they are required to be highly functional and to have high transmission speed and operation efficiency. Under operation, the various devices, such as a CPU, generate a great amount of heat, and the temperature of the devices increases correspondingly. As a result, the devices may become defective. Accordingly, the thermal dissipation capability of the product or the devices needs to be improved to maintain the efficiency thereof.
To dissipate the waste heat, a heat sink is normally disposed on the device, the discrete power or the logic integrated circuits. Accordingly, thermal interface materials play an important role in thermal management. To enhance the thermal communication between the device and the heat sink, thermal interface materials with the appropriate thermal conductivity and thermal resistance must be identified.
A typical thermal interface material is normally composed of a silicon resin, an aliphatic polymer, a low molecular polyester, an acrylic resin, wax or an epoxy type of phase change resin material. Metal or ceramic powders, such as aluminum nitride (AlN), boron nitride (BN), aluminum oxide (Al2O3), zinc oxide (ZnO) and artificial diamond are further added as the thermal conductive material.
In order for the thermal interface material to have the phase change characteristics, the base resin normally has a low molecular weight and a low melting point. However, this type of resin easily degrades under a repeated operation of the device, and the thermal stability of the resin becomes poor. Consequently, the contact area diminishes and the efficiency of thermal dissipation is greatly reduced.
Although metal or ceramic powders serving as the thermal conductive material have an acceptable thermal conductivity, the thermal conductivity of the thermal interface material is not significantly increased after the thermal conductive material is incorporated with the base resin. To increase the thermal conductivity of the thermal interface material, a large quantity of the metal or ceramic powders must be added (about 50 to 90 wt %). However, the increase of the amount of the thermal conductive material increases the interface thermal resistance, and the thermal dissipation efficiency of the entire packaged device is lower eventually. Consequently, the cost is increased. Accordingly, the conventional thermal interface material has a low thermal conductivity and a high thermal resistance.